Electrochemical Oxidation of Lignin to Value-Added Chemicals

Abstract

Lignin represents a significant waste in pulping mill streams, and is generally burned during the chemical recovery process to generate heat. However, its high heating value results in a bottleneck on the pulping process, and as the only renewable raw material for aromatic compounds, it is woefully underutilized as a heat source. Our work focuses on electrochemical oxidation of lignin-rich streams to generate value-added chemicals of industrial relevance. We have begun to investigate the mechanism of lignin oxidation, in which several proceeding chemical or electrochemical reactions are possible that influence the product distribution and depend on oxidation conditions. Because lignin is soluble in alkaline solutions, we are able to oxidize lignin on inexpensive, nonprecious metal electrodes. We will present voltammetric data that show the potentials at which lignin oxidizes, and will show GC/MS results that identify lignin oxidation products as a function of oxidation conditions (i.e., potential and time). We will present our work in elucidating the mechanism that lignin undergoes during electrochemical oxidation, with an eye toward controlling the oxidation products.